Process for the defluidization and fixed-bed coking of a preheated fluidized coal



NOV. 10, 1953 HQRNER 2,658,862

PROCESS FOR THE DEFLUIDIZATION AND FIXED-BED COKING OF A PREHEATED FLUIDIZED COAL Filed June 9, 1950 2 Sheets-Sheet 2 I :v vew TOR, HAROLD R. HORNER,

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Patented Nov. 10, 1953 PROCESS FOR THE DEFLUIDIZATION AND FIXED-BED COKING OF A PREHEATED FLUIDIZED COAL Harold R. Hurner, Indianapolis, Ind., assignor to Reilly Tar & Chemical Corporation, Indianapolis, Ind., a corporation of Indiana Application June 9, 1950, Serial No. 167,187

This invention relates to a process and also to an association of elements whereby coal may be fluidized preparatory to carbonizing in the process of making coke out of the coal. It is to be understood that the invention is not limited to the final carbonizing or coke making step, but deals primarily with the fiuidizing of the coal itself, whatever may be done with it thereafter.

However in the particular description of the one particular form of the invention as set out hereinafter, the invention will be described in reference to the making of coke in order to continue through one complete process. It has long been known that considerable time is required in order to transmit heat through a body of coal in a stationary and more or less compacted bed whereby the bed of coal may be first raised to the temperature at which the coal coalesces and reaches a plastic state, and finally solidifies into the carbonized or coked condition.

In the ordinary coking ovens, it has been customary to apply heat externally of the oven over a sufficiently long period of time to elevate the temperature of the contained coal for the coking operation. The long time required means of course that only a limited number of batches of coal may be put through the coking oven in a given amount of time. If it were possible to increase the rate of heating of the coal within the oven, it would naturally follow that the oven would be more serviceable in respect to being able to handle more batches of coal within the same amount of time. In other words for the same investment, a greater use of the oven may be had so that unduly large installations of numbers of the ovens may be avoided by using the ovens more frequently in order to get out more coke as well as the gases and other fluid products coming therefrom during the operations. In other words the problem resolves itself into a question of the rate of heat exchange from the heating medium to the coal itself.

A detailed description of the apparatus and the method of operating the apparatus in order to produce a more rapid rate of heat exchange is made in reference to the accompanying drawings in which Fig. 1 is a diagrammatic representation of the structure; and

Fig. 2 is a graph illustrating fluidized and nonfiuidized coal bed runs.

Coal of the desired quality is fed into a coal pulverizer I by any suitable means wherein the conveying of the coal to the pulverizer is through a conventional conveyer or even fed to the pul 1 Claim. (Cl. 202-22) verizer I by gravity. Here in the pulverizer I, the coal is heated by gas being taken from a furnace 2 by a blower fan 3 to carry the heated air or gas into the pulverizer was to warm the coal and at the same time tend to drive off some moisture.

In the pulverizer I, the coal is ground to a fineness of approximately sixty-five per cent passing through two hundred mesh screen. The air supplied by the blower 3 carries the heated and pulverized coal from the pulverizer I up through any suitable conveying means herein shown as a pipe 4, to discharge the pulverized coal into a dust separator 5. Here in the separator 5, the air is separated from the coal to be vented in any suitable means such as through the pipe 6. The pulverized coal settles into the bottom of the separator 5, and is stored therein.

A valve I at the underside of the separator 5 controls discharge of the pulverized coal therefrom. Where a batch operation is followed, the valve I will be intermittently opened and closed, but where a continuous operation is to be employed, the valve 1 will be open, and the pulver-- ized coal from the separator 5 may be flowed through a conductor 8, herein shown as being conveyed therethrough by gravity to a fluidizing chamber 9.

Thev fluidizing chamber 9 in its simplest form may consist simply of a, cylindrical steel shell I 0 having a grid or screen floor II extending across its lower end. The chamber 9 'is to be heated by any suitable means, internally or externally, herein shown as being internally heated fromthe furnace 2 whereby a pump I2 circulates a heat-, ing medium through the pipe I3 through an internal coil I4, the coil I I being'located centrally within the shell Ill. The flow of the heating me dium' is controlled by means of the valves I5 and I6 externally of the shell I0 and intercepting the pipe line I3, the valve I5 being on the pump discharge side and the valve I6 being on the pump intake side.

When the predetermined amount'of pulverized coal is taken from the dust separator 5 and discharged through the duct 8 into the chamber 9, and onto the perforated floor II, the valve 1 is closed off in the batch operation.

A fiuidizing gas which might be steam, the make-gas from the carbonization retort, flue gas, or even' gas secured from the pulverized coal within the fluidizing chamber, is fed into the shell III through the conical bottom H by any suitable means, herein shown as by a blower I8. The gas from whatever source it may be taken is flowed through the pipe IS in which there is a valve 20 to regulate the flow into the shell Ill in order to give the velocity within the fluidizing chamber 9 just sufiicient to fluidlze the coal. Where the fluidizing gas is to be introduced from outside of the system, --it --is entered into the system through thepip'e 2| under control of the valve 22. From the valve 22, the gas may be conducted through the pipe 23 through a heating chamber 24 and thence through the pipe 25 to the blower 18. The heater 24 may be supplied with heat from the furnace 2 by means of the pipe 26 controlled by the valve 2'! and the return pipe 28 controlled by the valve 29.

The gas entering the bottom of the chamber 9 is distributed uniformly over the diameter of this chamber by being diffused through the screen floor II. From the floor H, the gas passes up through the bed of the pulverized coal. Thevelocity of this gas coming into the chamber 3 is regulated as previously indicated by the'valve-lll so that the incoming gas in passing through the bed of coal will lift and separate the individual particlesof that coal'until-thecoal is separate one. particle from the other to fluidize that coal and carry the particles in suspension, one particle substantially separated from all adjacent particles,-to create a condition closely analogous to a liquid in respect to the coalitself That is, the condition may be pictured as being that each individual coal particle isbuoyedup by an encircling gas filmso that the particles are really in a state of high agitation something like the picture of the individual atoms within a molecule. In order to maintain this fiuidizedstate of the coal, the gas'entering'the chamber 9 is'allowed to discharge under pressure into a cyclone separator 31 so as to separate thedust from the coal within the chamber 9, drop the separated dust through the 'pipe 30,-and allow substantially clean gas to escape from the chamber through the pipe 32. At thesame'time, the interior of the chamber 9 is being'heated-by the coil [4 in the present instance to bring the temperature up to that point wherein the individual coal particles are heated'to just-below the'stage-where the coal will tend to-soften. The temperatureof 370 degrees C. is a good average, but each coal used will have a different softening range. In'any event, it is necessary'to stay just below'this' softening range of the coal because the-coal particles will coalesce in the fluidizing chamber to form 'a semiplastic mass which would be impossible to fiuidize satisfactorily. Therefore, the fluidization must stop justbefore thecoal'reaches this temperature of producingsoftening so that the' flui'dized and heated "coal may betransferred from the chamber 3. 'Ihat'is thetransfer from the chamber 9 is madewhileth'e coal is still 'in-its fluidized state.

During the 'fiuidizing step within the chamber 9, while the coil thus fluidized is beingheated. gases and vapors will be driven off from the'coal to appear within thechamber 9. These'gases along with the gas introduced through the valve 20 after being carried through the dust separator 31 in the upper end'of the chamber 9 are carried all through the pipe '32 where-the flow may be divided under control of the valve #33 anda second valve 34. The-valve'33controls a flow from the pipe-32 to a pipe 35 which leads to a gas scrubber 36being of any-conventional design. scrubbed gasmay escape from the pipe 31, and liquids may be conveyed from the scrubber through'the'pipe38.

that the gas coming from the pipe '32 is then at a relatively high temperature so that it can be conveyed directly through the floor II and back into the chamber 9 without much additional heat if any having'to be applied to that recirculating gas.

As indicated, the gas and vapors such as water vapor, inaccess of the amount required for fluidization is bled off through the valve 33 and passed through the scrubber 36 for recovery of the desired elements thereof.

'By reason of the fluid state of the pulverized coal within the chamber 9, heat transfer is rapidly efiected from the coil [4 to the individual coal particles, by all three-possible-means such as by conduction, convection, and by radiation. By reason of the highly agitated-mass,=-and by reason of the nature of the fluidized coalbeing somewhat in the nature of a liquid, the heated particles circulate-through the entire mass to effect the transfer of heat very quickly.

The fluidized and heated coal is discharged from the chamber 9 after it has reached the-temperature just below the coalescing temperature range, to be carried out through the duct orpipe 39 in which there is placed acontrol valve. This pipe 39 may lead to any desired type of a carbonizing or coking retort, herein conventionally shown in one form as-acoking retort 4 I. The heated, fluidized coal, is dischargedthroughthe hatchways 42 into the 'carbonizing chamber 43.

The coal entering thechamber-43 in-itsfluidized state will tend to settle to its original volume, and the contained gas escapesand is taken oil in the usual manner through a vent pipe to be carried to-aconventional gas handling system. The chamber 43 is heated as in anycarbonizing retort, the initial heating tending to drive off the gas from the coal from its surface to aid-in the settling of the coal.

When the coal has been reduced toitssubstantiallyoriginal volume within theretort 4 l car bonization of the coal continues by the application of heat to bring the coal up to higher temperatures the temperature being-carried upto aroundfive'hundred and eighty degrees-C although this temperature of course will varyin accordance with the coal again, but in any event the carbonization is considered complete when the coal charge reaches "a ,pre-determined temperature'for the particularcoal bein'g treated.

Now while the-coal in the retort is in substantially the same volume as it-would'have been had it been put in the retort originally without being fluidized, there is a great'saving of time in the time dwell of the carbon "material Within the retort as compared 'to'fiuidizing and nonfiuidizing the coal.

The great advantage of operating a 'cok-eoven with a fluidized charge over operating the same kind of an oven with a stationary charge is 'set out in Fig. 2. The lines A and B show the fluidizing operation while the lines C and D show the-standard stationary charge operation.

In the chart, Fig. 2, that part of the'solid line to the left of the zero vertical line represents the fluidizing and pre-heating operation of the coal up to a point short of 400 degrees'C. From that point, the fluidized coal is transferred'into'the coke oven. The continuing line A represents temperatures taken at the various time intervals within the coal, inside of the coke oven, close to the heating walls. The broken line 13 represents the temperature in substantially the center of the charge in the oven.

The line C represents or indicates temperatures taken at the time intervals indicated close to the heating walls within the oven of the stationary charge operation, while the line D indicates the temperatures taken within substantially the center of the stationary charge within the coke oven.

It is to be noted that the rate of climb of the fluidized coal upon being introduced into the coke oven and the rate of climb of temperature of the stationary charge in the standard operation run are at about the same rate. It is to be kept in mind that these temperature indications plotted on these portions of the lines represent the temperatures near the heating walls or" the coke oven. However it is to be noted that the temperatures indicated by the lines C and D have an extremely wide spread as compared to the spread between the lines A and B. The line D very clearly indicates that a great amount of time required in the standard sixteen hour cycle for the stationary charge operation of a coke even is taken up in bringing the stationary charge up to the four hundred degree C. temperature. In other Words it takes substantially eight hours constant heating to bring the temperature of the coal in its central zone up to that point Where it will start heating above the one hundred degree C. temperature. Then there is a gradual rise in the time from the initial eight hour period up to the thirteen hour period or a little therebeyond, which is substantially at the four hundred degree C. temperature when the central zone temperature will start to increase rapidly up to the end of the sixteen hour period. There is a tremendous amount of heat required to be transferred from the Wall of the oven through the stationary charge to evaporate the water content, and when this heat has to be transferred through seven or eight inches of coal to the central zone of the charge, the delay indicated by the chart follows. Now this is not true in the fluidized heating through this zone.

That delay is overcome by the fiuidizing of the coal and the pre-heating of the fluidized coal before it is put into the pre-heated coke oven. Thus it is to be seen that as the example indicates in Fig. 2, there is the tremendous saving of time in the operation of the standard by-product coke oven resulting in a saving of nearly nine hours.

The yield of products such as gas, tar, coke, and other well known products, are comparable with the products obtained when carbonizing the same coal non-fluidized under the same retort operating conditions. In the fiuidizing operation as above indicated, some of those products will be recovered prior to the carbonizing step in the retort.

Therefore it is to be seen that the system set up and the manner of its operation produce an extremely and highly beneficial result in that the use of the retort itself for the carbonizing step is reduced in time practically one-half of what it is in use in the conventional procedure. The cost of the apparatus and its operation for fluidizing the coal prior to flowing it into the retort is quite minimal as compared to the cost of building and operating additional retorts. While we have herein shown and described the invention in best form as now known to us, it is obvious that many structural changes may be employed in the system itself, and variations may be introduced in the method of operation all without departing from the spirit of the invention, and we therefore do not desire to be limited to that precise structure or method beyond the limitations which may be imposed by the following claim.

I claim:

In a process of producing a structurally dense, hard metallurgical coke from coal and securing a maximum yield of undecomposed by-products, those steps of heating the individual, discrete particles of finely ground coal in a fluidized state to a temperature immediately under its coalescing temperature range; conveying in suspension the heated fluidized coal beyond influence of continued fiuidization directly into a heated confined retort; and heating the coal in said retort by indirect heating so as to defiuidize said coal by driving ofi fluidizing gas and continuing heating said coal through a plastic state to a coked state.

HAROLD R. HORNER.

References Cited in the file of this patent UNITED STATES PATENTS Date Number Name 1,775,323 Runge Sept. 9, 1930 1,805,109 Runge May 12, 1931 1,907,569 Parr et al. May 9, 1933 1,909,421 Parr et a1 May 16, 1933 1,984,380 Odell Dec. 18, 1934 2,131,702 Berry Sept. 27, 1938 2,167,100 Benezech July 25, 1939 2,379,077 Harding June 26, 1945 2,408,810 Puening Oct. 8, 1946 2,444,990 Hemminger July 13, 1948 2,449,635 Barr Sept. 21, 1948 2,462,366 Davies, Jr. et al Feb. 22, 1949 2,471,119 Peck et a1 May 24, 1949 2,516,974 Garrison Aug. 1, 1950 FOREIGN PATENTS Number Country Date 508,648 Germany Sept. 29, 1930 OTHER REFERENCES Chemistry of Coal Utilization, vol. I, pages 848-862. H. H. Lowry, John Wiley and Sons. 

